Snoop has found another hint: Ask your Pinners or your readers to participate or engage with your pin. This is done by actually asking your readers/pinners to act. It's referred to as "a call to action"... having your pinners do some specific action.
And since most of us are not mind readers, they must be told 'what to do'. If you don't tell your readers/ pinners what to do, how will they know?
By giving the pinner a direction or compelling them to act might be all that they need to visit your site.